Cannulas are generally used in endoscopic surgical procedures which enable closed surgery to be performed via portals. A variety of elongated instruments may be passed through the portals to gain access to an internal surgical work site (e.g., a knee, a shoulder, etc). Very often a disposable cannula is inserted into the portal in order to provide a convenient passageway through which various instruments may pass.
Because many arthroscopic procedures require the use of pressurized fluid to distend and irrigate the joint being operated upon, the cannula must provide a sealed passageway in order to enable instruments to be passed into and out of the cannula while maintaining a fluid seal to prevent squirting whether or not an instrument is in the cannula passageway. The sealing of such cannula passageways is usually accomplished by one or more membranes attached to the proximal end of the elongated cannula.
Some prior art devices utilize two different sealing mechanisms: one optimized for sealing when no instrument is present in the cannula and another optimized for sealing while an instrument is present.
Prior art cannulas are also generally rigid and inflexible, and since the portals through which endoscopic surgery is performed are desired to be as small in diameter as possible, the inner flanges of such cannulas are generally not wide enough to provide the optimum amount of stability while instruments are being transferred therethrough. Accordingly, there is a need in the art for an improved cannula with a wider and more stable inner flange. There is also a need for a cannula that can be inserted into the body using a minimally invasive insertion tool through a portal. Further, there is a need in the art for a cannula that has two fluid seals, or dams; a first dam to prevent fluid from squirting from within the body when instruments are passing through the cannula, and a second dam to prevent fluid from squirting when the cannula is being inserted within the portal. A cannula designed with a stop gap measure to prevent the possibility of over insertion in the body is also needed.